The employment of satellites for communications and navigation purposes so far has been mainly marked by the use of individual or a few satellites, which are only in contact via microwave radio channels with the earthbound operator, or respectively user. However, in the future, increasingly larger groups of satellites will be placed in earth orbit for the same purpose, such as for communications systems, partially in the realization phase, which circle the earth at low altitudes. Their limited visibility requires the permanent forwarding of an earthbound user between a plurality of continuously passing satellites.
Maintaining communications past the area of visibility of a satellite takes place by the conveyance of information between the individual satellites of such a system which, for reasons of weight and space, most advantageously takes place in an optical manner. Considerable optical output is required here with fiber-optic communications, although in comparison with the output required for a microwave connection, it is still relatively low.
Diode-pumped solid-state lasers are advantageous because of the great coherence of their light emission, provided particularly energy efficient coherent transmission methods are used. With a high modulation bandwith, the external modulation of the phase of the light emitted by the laser required in this case must be performed by means of a modulator designed in the form of an optical waveguide, which cannot be operated at a high optical output. The transition from a solid-state laser emitting a collimated beam into a waveguide structure is considered to be critical and prone to losses, because of which an additional output reserve is required in the subsequent quantum-optical amplifier. The design of the later as a solid body amplifier involves further technical problems.
Thus, for a considerable utilization of the optical pump output generated by the diode lasers, it is necessary to provide a multitude of passages of the light to be amplified through the optically pumped zones of the solid body, which results in relatively large, high-mass and acceleration-sensitive apparatus. A mechanical temperature-stable acceleration-resistant structure is required in order to prevent the overlapping of pump light and signal light beams by external influences.